On Wed, 2012-11-28 at 18:24 -0500, Jerome Glisse wrote: > On Wed, Nov 28, 2012 at 6:18 PM, Thomas Hellstrom <thomas@xxxxxxxxxxxx> wrote: > > On 11/28/2012 04:58 PM, j.glisse@xxxxxxxxx wrote: > >> > >> From: Jerome Glisse <jglisse@xxxxxxxxxx> > >> > >> This patch add a minimum residency time configurable for each memory > >> pool (VRAM, GTT, ...). Intention is to avoid having a lot of memory > >> eviction from VRAM up to a point where the GPU pretty much spend all > >> it's time moving things in and out. > > > > > > This patch seems odd to me. > > > > It seems the net effect is to refuse evictions from VRAM and make buffers go > > somewhere else, and that makes things faster? > > > > Why don't they go there in the first place instead of trying to force them > > into VRAM, > > when VRAM is full? > > > > /Thomas > > It's mostly a side effect of cs and validating with each cs, if boA is > in cs1 and not in cs2 and boB is in cs1 but not in cs2 than boA could > be evicted by cs2 and boB moved in, if next cs ie cs3 is like cs1 then > boA move back again and boB is evicted, then you get cs4 which > reference boB but not boA, boA get evicted and boB move in ... So ttm > just spend its time doing eviction but he doing so because it's ask by > the driver to do so. Note that what is costly there is not the bo move > in itself but the page allocation. > > I propose this patch to put a boundary on bo eviction frequency, i > thought it might help other driver, if you set the residency time to 0 > you get the current behavior, if you don't you enforce a minimum > residency time which helps driver like radeon. Of course a proper fix > to the bo eviction for radeon has to be in radeon code and is mostly > an overhaul of how we validate bo. > > But i still believe that this patch has value in itself by allowing > driver to put a boundary on buffer movement frequency. > > Cheers, > Jerome So, a variation on John Carmack's recommendation from 2000 to use MRU, not LRU, to avoid texture trashing. Mar 07, 2000 - Virtualized video card local memory is The Right Thing. http://floodyberry.com/carmack/johnc_plan_2000.html In fact, this was last discussed in 2005 with a patch for a 1 second stale texture eviction and I (still) wondered why a method it was never implemented since it was an clear problem. http://thread.gmane.org/gmane.comp.video.dri.devel/17274/focus=17305 -- Alan. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
